Open source IGBT Gate Driver

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This is a beta version of open source high power IGBT Gate Driver, although many features has been tested on other drivers this one is not tested yet, so use it at your own risk under GPL v3

link on GitHub : Open source IGBT gate driver

Features

here you can find features of this open source IGBT gate driver, each feature will be linked to its own post

  1. Short pulse suppression
  2. Under voltage protection
  3. IGBT Fault soft turn off
  4. Active VCE clamp of IGBT
  5. Separate Ron and Roff for Gate
  6. VCE monitoring
  7. High side IGBT-Low side IGBT shoot thought protection (not tested yet)
  8. Adjustable VCE protection (this version of gate driver as been set for SKM200, check tutorial for other IGBT’s )
  9. Mosfet for IGBT gate clamp when switch is off

To add:

  1. dynamic short-circuit protection
  2. Designing its own converter

Modes of operations

This gate driver performs four operating modes:

  • Turn-on
  • Turn-off
  • Over-current protection
  • Active Vce clamping

Gate Driver Turn-on mode :

transistors Q1 and Q2 were closed when photo-coupler U3 is turned on by input signal, let the voltage of Q8,Q9 base to increased to 24V. therefore, Q8 and Q11 is ON while Q9 and Q12 are OFF, consequently, IGBT turned on immediately, and collector voltage dropped to (1.8->3.2)V for SKM200GB12E4.

Gate Driver Turn-off mode:

Q1 and Q4 turned on when U3 is OFF, which led Q8 and Q11 turned off while Q9 and Q12 turned on. The voltage of Gate pin dropped to OV rapidly, 8V lower than of the Emitter pin which is biased to 8v by D10 , and caused IGBT turned off reliably.

Gate Driver Over-current protection mode:

when IGBT was ON, the voltage of D16 cathode kept around 10.5V (Vd15 + Ve + Vce), and V c38 kept around 24V. If short-circuit or over-current occurred, IGBT would withstand high current and goes to desaturation state, then Vce increased rapidly, led D15 turned off. The voltage of D16 cathode increases to 13V until d16 breaks down, and then Q3 turned on. C38 discharged through R23 and Q3, which causes the voltage of “on” label drop gradually, and turn the IGBT off slowly.

Gate Driver Active Vce clamping mode:

IGBT modules and converter circuits have parasitic inductances that can’t be completely eliminated; their influence on system behavior also can’t be ignored.

Figure 1 illustrates the parasitic inductances contained in a commutation circuit. The current change caused by turning off the IGBT produces an overshoot voltage at its collector terminal, as shown in Figure 2.

The commutation speed (and therefore, the turn-off overvoltage) at an IGBT can, in principle, be affected by the turnoff gate resistance Rg(off). This technique is used particularly at lower power levels. However, the Rg(off) must then be matched for overload conditions, such as turn-off of the double-rated current, short circuit, and a temporarily increased link circuit voltage.

In normal operation:

this results in increased switching losses and turn-off delays, which reduces the usability or efficiency of the modules. As a result, this simple technique is unsuitable for modern high power modules.
little fuse active vce
When IGBTs are driven with a pulse that is shorter than the response time in the event of a short circuit, the fault is not detected and the driver turns off too quickly.

The resulting overvoltage destroys the IGBT. Moreover, coverage of limit cases (between overcurrent/non-overcurrent) presents a problem; for instance, a higher overvoltage may well occur when the double-rated current is turned off than at a short-circuit turn-off **
VCE active clamp
The feedback branch consists of a clamping element, which, as a rule, is made up of a series of transient voltage suppression (TVS) diodes. If the collector-emitter voltage exceeds the approximate breakdown voltage of the clamping element, a current flows via the feedback to the gate of the IGBT, raising its potential, so that the rate of change of the collector current is reduced, producing a stable condition. The voltage across the IGBT is then determined by the design of the clamping element.

The IGBT operates in the active range of its output characteristic and converts the energy stored in the stray inductance into IGBT heat.

The clamping process continues until the stray inductances have been demagnetized. The fundamental relationships involved here on the basis of typical curves are illustrated in the lower part of Figure 5.

A single high voltage TVS diode, or several lower voltage TVS diodes connected in series with a resultant high voltage, can be used to provide active clamping based on the DC power line voltage or IGBT Vce voltage. for further details read Littlefuse Application note 

VGE before clamping is like the picture below


VGE before active clamping
at voltage of five TVSs dynamic clamp starts and current goes from capacitor C57 to gate until it charges up the Vge is like picture below
Vge dynamic clamping
if overshoot voltage goes higher than all TVSs voltage then static protection starts and VGE is going to be like picture below
VGE static clamping

Clamping of IGBT collector voltage is shown HERE on YouTube note : Video is in Persian and oscilloscope probe is on 10x

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Emad Bahra
emad@bahra.ir

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